1. Field of the Invention
The invention generally relates to the field of photography. More particularly, it relates to a dual lens camera of the type wherein a relatively longer focal length lens and a relatively shorter focal length lens are selectively used to expose film in the camera, for example to take a telephoto or a wide angle picture.
2. Description of the Prior Art
A dual lens camera typical of the prior art is partially illustrated in FIG. 1 of the accompanying drawings. The camera has a relatively longer focal length lens 1 and a relatively shorter focal length lens 3, either one of which is selectively used for telephoto and wide angle photography. A fixed mirror 5 is permanently located behind the longer focal length lens 1, and a movable mirror 7 is positionable behind the shorter focal length lens 3 in facing parallel relation to the fixed mirror. The movable mirror 7 in this position has a matte black coating 9 on its rear side which is disposed to block ambient light entering the shorter focal length lens 3 to prevent the light from reaching an exposure plane 11 (also referred to as a film plane) proximate a rear door 13 of the camera. In addition, the two mirrors 5 and 7 define a Z-shaped light-ray path (i.e., one that bends at angles of less than 90.degree.) X, Y, Z from the longer focal length lens 1 to the exposure plane 11. Alternatively, the movable mirror 7 may be pivoted in a clockwise direction in FIG. 1 about a mounting pin 15, out of its blocking position behind the shorter focal length lens 3 to a non-blocking position depicted in broken line, to allow ambient light entering the shorter focal length lens to pass straight through to the exposure plane 11. In the non-blocking position, the movable mirror 7 deflects ambient light reflected by the fixed mirror 5 from the longer focal length lens 1 to prevent the light from reaching the exposure plane 11. Thus the alternate positions of the movable mirror 7 determine which one of the two lenses is used.
In the dual lens camera partially illustrated in FIG. 1, a shutter and/or aperture plane defining plate 17 is disposed with respective open portions 19 and 21 of the plate optically aligned with the longer and shorter focal length lens 1 and 3. The plate 17 is located between the two lenses 1 and 3 and the exposure plane 11, and it is supported parallel to the exposure plane and a front face 23 of the camera. Since the longer focal length lens 1 is greater lengthwise than the shorter focal length lens 3, the arrangement of the plate 17 parallel to the exposure plane 11 appears to necessitate a front to rear dimension D of the camera that prevents making the camera very compact in size.